Measuring Photoacid Distribution at Nanoscale now Possible with Fluorescence Technique

23 April 2013

A group of researchers have used a fluorescence technique to track the the nanoscale distribution of photoacid molecules in photoresists, the National Institute of Standards and Technology (NIST) has said on its website. The technology, originally created to show biological cells with a size smaller than the wavelength of weight, could pave the way for producing smaller electronic devices and even allow for measuring nanoscale transport processes in other system such as polymers.

The experiment was conducted by researchers from the NIST Center for Nanoscale Science and Technology, the University of Maryland and Korea University, who used a new fluorescent dye to better examine the location of photoacid molecules. These novel fluorescent compounds have the property to appear dark or bright when exposed to ultraviolet light or by reacting with an acid molecule located a short distance away. Over a certain period of time, they fit the fluorescent signal of each dye molecule to a two-dimensional distribution, which allowed the researchers to plot the locations of the photoacid molecules with single-molecule sensitivity. The team also succeeded in collecting high-resolution information even when fluorescent molecules are present at very low concentrations through a newly-developed statistical analysis techniques. The technology can guarantee that the system's behaviour is unaffected by the fluorophores present.

This innovative method could provide for a more precise observation of photoacid molecules in photoresists because the current distribution of such molecules within resist films restricts the minimum features sizes that can be produced on computer chips. Until now, experts have only been able to conclude indirectly where the production of photoacid molecules takes place and how they diffuse by looking into resist images after the resist is fully exposed.